It is known that electromagnetic communication systems employ broad bandwidth techniques, such as the so-called frequency-agile or frequency-hopping systems in which both the transmitter and receiver rapidly and frequently change communication frequencies within a broad frequency spectrum in a manner known to both units. When operating with such systems, antennas having multiple matching and/or tuning circuits must be switched, whether manually or electronically, with the instantaneous frequency used for communications. As such, it is imperative to have a single antenna reasonably matched and tuned to all frequencies throughout the broad frequency spectrum of interest. Although the art discloses such broad-band antennas, these antennas suffer from a somewhat limited frequency range.
The user therefore has to use a plurality of antennas distributed all over the vehicle platform to be able to use the entire radio frequency spectrum. To minimize the number of antennas, a method is needed to encompass all these antenna functions in a single antenna system occupying a single antenna mounting location. The challenge is to vertically stack one on top of the other, feed signals to each, and electrically isolate the entire assemblage of co-located antenna elements.
U.S. Pat. No. 6,429,821 entitled Low Profile, Broad Band Monopole Antenna With Inductive/Resistive Networks and U.S. patent application Ser. No. 13/383,271 entitled Low Profile, Broad Band Monopole Antenna With Heat Dissipating Ferrite/Power Iron Network And Method For Constructing The Same, both of which are incorporated herein by reference, describe antennas with 25 to 512 MHz antenna functions. U.S. Pat. No. 7,855,693 entitled Wide Band Biconical Antenna With A Helical Feed System, which is also incorporated herein by reference, describes an antenna with a 300 to 2700 MHz antenna function utilizing a helical feed system. However, no known antenna system provides functionality over radio frequency bands covering 30 to 512 MHz, and 500 to 2500 MHz separately as two signal input ports at the base of the antenna. Therefore, there is a need in the art for an antenna system which combines the aforementioned antenna functions into a single antenna system occupying one antenna position on a vehicle while inherently providing an elevated position for a VHF/L-Band element array.